Multi-functional graft and derivatized polymers or copolymers for lubricating oil compositions are well known. In general, a hydrocarbon solution of a polymer substrate, as for example a copolymer, terpolymer or higher polymer base, is reacted with an olefinic carboxylic material in a graft reaction to prepare a grafted polymer. This is then further functionalized by a reaction with a variety of compounds to produce an oil concentrate of the multi-functional polymeric additive. The oil concentrate will generally contain from about 5 to 35 weight percent of the multi-functional polymeric additive based on the total weight of the mixture. Ethylene copolymers which have been grafted with maleic anhydride and then functionalized with an amine compound represent one class of multi-functional lubricant additive. Examples of grafted and derivatized multi-functional additives may be seen in U.S. Pat. No. 4,146,489 to Stambaugh et al., U.S. Pat. No. 4,114,181 to Elliott et al. and U.S. Pat. No. 4,089,794 to Engel et al.
A serious problem which has been encountered with oil concentrates of certain high molecular weight grafted and derivatized polymers and copolymers is their very high bulk viscosity. Bulk viscosities determined as the Kinetic Viscosity at 100.degree. C. of over 2000 Centistokes have been observed relative to the identical underivatized polymer with a Kinetic Viscosity at 100.degree. C. of less than 100 Centistokes. Some of the graft and derivatized copolymers are so viscous that their bulk viscosity cannot be measured. The high bulk viscosity of these product concentrates makes them extremely difficult to handle, process and/or transport and this is a serious drawback to their usefulness.
A method has now been found for substantially reducing the high bulk viscosity of oil concentrates of high molecular weight graft and derivatized polymers and copolymers greatly enhancing their usefulness as lubricant additives.